The instant invention relates to hingeable plate assemblies of the general type used for photolithographic processes and more particularly to a latching assembly for automatically latching the lid plate thereof in an open position.
Photolithographic processes have generally been found to be highly effective for use in forming relief patterns on various substrates, such as on printed circuit boards. In this regard, typical photolithographic processes are carried out by applying a mask image to a glass plate, and then overlaying the glass plate on a substrate which has been previously coated with a photosensitive material. The unmasked areas of the substrate are then exposed to actinic radiation in order to effect the desired reaction in the photosensitive material thereon. The glass plate is removed and the substrate is treated with a solvent developing process to produce the desired relief image on the substrate.
Similar processes have also been found to be effective for simultaneously applying images to both sides of a substrate utilizing a hingeable glass plate assembly comprising a pair of masked plates which are hingeably connected. A process of this type is carried out by positioning a substrate between a pair of glass plates having mask images thereon and simultaneously exposing both sides of the substrate which have been previously coated with a photosensitive material. Thereafter, both sides of the substrate are treated with the solvent developing process to produce the desired relief patterns thereon.
During repeated exposures of numerous substrates it has generally been found that repeated positioning of the substrates between the glass plates is an awkward procedure which requires that the lid plate be raised and manually held in an open position while the resident substrate is removed and a new substrate positioned. Manually holding the lid plate open ties up one of the operators hands while attempting to remove the resident substrate and reposition another with the other free hand. One solution to this problem which has been heretofore available is the provision of a swinging prop arm which holds the lid plate open while the substrate is replaced. However, the operator still has to manually position the prop arm before attempting to remove the substrate from the plate assembly and this has also been found to be an awkward procedure. In addition, it has been found that the prop arm can slip or become dislodged during substrate replacement and cause the lid plate to fall downward onto the operators hands. The heretofore available plate assemblies have thus been found to be inadequate in these regards.